Carburetor with altitude and t-mecs metering control

ABSTRACT

A carburetor for an internal combustion engine with a tri-mode emission control system having the main fuel metering rod thereof positioned by a power piston responsive to manifold vacuum controlled by a fluid pressure responsive valve and its travel is limited by a pair of integral stops positioned by an aneroid and a fluid pressure responsive actuator, the flow of the pressure fluid to both the valve and to the actuator being controlled as a function of the operating mode of the emission control system as effected by either engine speed or operating temperature whereby the carburetor is operative to provide dual range fuel metering with compensation for altitude.

United States Patent 1 [111 3,912,796 Brown, III Oct. 14, 1975 CARBURETOR WITH ALTITUDE AND 3,744,346 7 1973 Miner et a1. 261/D1G. 74

T MECS METERING CONTROL 3,807,172 4/1974 Masaki 3,859,397 1/1975 Tryon 261/121 B [75] Inventor: Reed M. Brown, Ill, Fairport, NY. [73] Assignee: General Motors Corporation, Primary Examiner-"Tim Miles Detroit, Mich Attorney, Agent, or FzrmArthur N. Krein [22] Filed: May 10, 1974 [57] ABSTRACT 1 1 pp 468,756 A carburetor for an internal combustion engine with a tri-mode emission control system having the main fuel [52] Us. Cl 261/39 261/69 261/DIG' metering rod thereof positioned by a power piston re- 123/119 sponsive to manifold vacuum controlled by a fluid [5]] Int Cl 2 FOZM 7/20 pressure responsive valve and its travel is limited by a [58] Fie'ld R 39 A pair of integral stops positioned by an aneroid and a I I I 261/1316 I23, 19 fluid pressure responsive actuator, the flow of the pressure fluid to both the valve and to the actuator [S6] References Cited being controlled as a function of the operating mode UNITED STATES PATENTS of the emission control system as effected by either engine speed or operating temperature whereby the 3,01 1,770 12/ 1961 Stoltman 261/69 R carburetor i Operative to provide dual range fuel gamer tering with compensation for altitude. t evern 3,685,502 8/1972 Oberdorfer, Jr. 26l/DIG. 74 5 Claims, 11 Drawing Figures 27 SOL-l HIGH TEMP.

ENgLliE SPEED NO. SW-l US. Patent 001;. 14,1975 Sheet 1 Of3 3,912,796

50 5 COMPOSITE W013i;

AIQR RATE U.S. atent a. 14, 1975 Sheet 2 of3 3,912,796

COMPOSITE vv.o. ll/I AIR RATE COMPOSITE wo. M 2/:

929.8 AIR RATE Patent Oct. 14,1975 Sheet3 0f3 3,912,796

CARBURETOR WITH ALTITUDE AND T-WCS METERING CONTROL This invention relates to a fuel metering control in a carburetor for an internal combustion engine and, in particular, to a linkage style altitude and T-MECS metering control for a carburetor.

It has recently been disclosed in copending U.S. Pat. application Ser. No. 312,574, now U.S. Pat. No. 3,824,788 entitled Internal Combustion Engine and Method of Operation for Exhaust Emission Control filed Dec. 6, 1972 in the names of Edward N. Cole and George W. Niepoth and in U.S. Pat. application Ser. No. 312,567, now U.S. Pat. No. 3,823,555 entitled lnternal Combustion Engine and Method of Operation for Exhaust Emission Control filed Dec. 6, 1972 in the name of Edward N. Cole, both assigned to the same assignee as of this application, that exhaust emission from the internal combustion engine of an automotive vehicle can be effectively controlled by a method of emission control operation using selectively either a catalytic converter or a reactor in the exhaust system of the engine. As disclosed in the above-identified U.S. Pat. application Ser. No. 312,574 and in U.S. Pat. application Ser. No. 312,567, the method of operation for i'm proved exhaust emission control includes three modes of operation of the exhaust system emission control components and is appropriately identified as a trimode emission control system or simply T-MECS.

The three modes of operation for exhaust emission control are identified and defined, as follows: A warmup mode, which may take about one minute, in which air is injected at the combustion chamber exhaust ports of the engine to promote an oxidizing reaction in the exhaust gases, the exhaust gases then being directed through the catalytic converter units of the exhaust system (generally after heating the inlet manifold) to heat the converter units. A converter mode in which exhaust gases are directed to one or more converter units and pass in a reducing atmosphere through a portion of the converter units having a reducing catalyst, air being injected into the exhaust gases leaving the reducing portion and the exhaust gases then pass in an oxidizing atmosphere through a portion of the converter units containing an oxidizing catalyst. A reactor mode in which air is injected at the combustion chamber exhaust ports to support an oxidizing reaction in the exhaust manifold reactors and exhaust flow through the converter units is avoided to protect the catalyst.

It has also been proposed in the above-identified U.S. Pat. applications Ser. No. 312,574 and Ser. No. 312,567 that during the converter mode of operation, the carburetor should supply an air-fuel mixture to the engine which is richer than stoichiometric to provide a reducing atmosphere in the reducing portion of the; converter unit. During the reactor mode of operation, when emissions are controlled in the manifold reactors rather than in the catalytic converter units, it would be desirable for the carburetor to supply an air-fuel ratio which is leaner than stoichiometric. A carburetor operating in the manner described above would improve fuel economy, reduce the combustibles which must be treated in the manifold reactors, and provide part or all of the oxidizing atmosphere in the reactors.

As is well known, a conventional four-barrel, twostage carburetor, for example, is provided with an idle system, a main metering system and a power enrichment system for controlling fuel flow to the engine during various operating conditions of the engine. The main metering system of such a carburetor includes at least one tapered or stepped metering rod operating in a main metering jet orifice to control flow of fuel to the engine, the position of the metering rod being controlled by a power piston responsive to manifold vacuum.

A carburetor for use with an engine utilizing the trimode emission control system should, however, as described above, be capable of supplying a rich fuel mixture during the converter mode of operation, a leaner mixture during the reactor mode of operation, while still permitting full power mixtures to be supplied to the engine during heavy load or high speed engine operation. in addition, for use in such a tri-mode emission control system, it would also be desirable to have the carburetor maintain the desired fuel mixtures during the converter mode and reactor mode of operation substantially constant during vehicle operation at various altitudes.

It is therefore a primary object of this invention to provide a linkage style altitude and tri-mode emission control system metering control for the main metering rods of a carburetor whereby fuel flow to the engine is controlled as a function of barometric pressure and the mode of operation of the emission control system for the engine.

Another object of this invention is to provide a control for the main metering rods of a carburetor for an internal combustion engine whereby the range of movement of the power piston controlling the movement of the main metering rods is limited as a function of barometric pressure and the operating mode of the tri-mode emission control system for the engine.

A further object of this invention is to provide a carburetor for an internal combustion engine in which the main metering rods of the carburetor are positioned by a power piston responsive to manifold vacuum controlled by a fluid pressure responsive valve and the travel of the power piston is limited by a pair of stops positioned by an aneroid and a fluid pressure responsive actuator, the operation of the valve and of the actuator being controlled as a function of the operating mode of a tri-mode emission control system for the engine.

A still further object of this invention is to improve a carburetor, for use on an engine with T-MECS, whereby the carburetor provides dual range main fuel metering with altitude compensation to provide the proper air-fuel ratio when the emission control system is operating in the converter mode and to provide optimum economy when operating in the reactor mode.

These and other objects of the invention are obtained in a carburetor having one or more main metering rods positioned by a power piston responsive to manifold vacuum by providing a fluid pressure responsive valve to permit the flow of manifold vacuum to the power piston during only one mode of operation of the emission control system for an engine and by limiting the travel of the power piston by means of movable stops positioned by an aneroid and a fluid pressure responsive actuator connected together in series.

For a better understanding of the invention, as well as other objects and further features thereof, reference is had to the following detailed description of the invention to be read in connection with the accompanying drawings, wherein:

FIG. 1 is a schematic illustration of a linkage style altitude and T-MECS metering control, in accordance with the invention, for the carburetor of an engine, the

elements thereof being shown when operating at sea level and in a converter mode;

FIG. 2 is a graph of the air-fuel ratio vs. air rate to the engine with the elements of the metering control operating as shown in FIG. 1;

FIG. 3 is a view similar to FIG. 1 but showing the position of the elements during operation at sea level and in the reactor mode;

FIG. 4 is a graph of the air-fuel ratio vs. air rate to the engine with the elements of the metering control operating as shown in FIG. 3;

FIG. 5 is a view corresponding to FIG. 1 but showing the position of the elements when operating at 5,000 foot altitude and in a converter mode;

FIG. 6 is a graph of the air-fuel ratio vs. air rate to the engine with the elements of the metering control operating as shown in FIG. 5;

FIG. 7 is a view corresponding to FIG. 1 but showing the position of the elements when operating at 5,000 foot altitude and in a reactor mode;

FIG. 8 is a graph of the air-fuel ratio vs. air rate to the engine with the elements of the metering control operating shown in FIG. 7;

FIG. 9 is a top view of a portion of a four-barrel carburetor with parts removed to show the structural details of the linkage style altitude and T-MECS control system of the invention;

FIG. 10 is a sectional view taken along line 10-10 of FIG. 9; and,

FIG. 11 is a sectional view taken along line 1111 of FIG. 10.

With reference first to FIGS. 1, 3, 5 and 7, a main metering rod 10 of a carburetor is positioned in a main metering well 11 in the float bowl housing 12 of the carburetor to operate in a main metering jet orifice 14 to control fuel flow to an engine, not shown, in a conventional manner well known in the art. A metering rod carrier 15 is connected to a main power piston 16 and to the metering rod 10 to position the metering rod in accordance with the axial position of the power piston 16. Power piston 16 is slidably journalled in a piston bore 17 in the housing 12 and is biased in one direction by a piston spring 18. Movement of the power piston 16 in the opposite direction is effected by differential pressure acting on opposite sides of the piston, as by connecting the lower end of the piston bore 17 to engine manifold vacuum and having the other end in communication with the atmosphere.

In the conventional operation of a main metering system, the metering rod 10 is either held down to effect a minimum flow area through the metering jet orifice 14 or it is raised in accordance with falling engine vacuum to increase the flow area to some area intermediate the minimum flow area and a niaximum flow area. The metering rod 10 is held down to effect minimum flow area when the magnitude of manifold vacuum is sufficient to overcome the upward bias of the piston spring 18 on the power piston 16 so that the power position is moved to its lowermost position. Should the manifold vacuum fall as the absolute pressure therein increases, the pressure differential on the opposite side of the power piston 16 decreases to a point where the effect of vacuum on one side of the power piston is overcome by the upward bias of the spring 18. As the vacuum falls below that required to hold the power piston 16 in the position to effect minimum flow area, the spring 18 moves the power piston upwards to retract the tapered or stepped portion of the metering rod 10 to increase the flow area through the orifice 14 above the minimum flow area.

Now, in accordance with one feature of the subject invention, the piston bore 17 communicates via a coaxial passage 20 and a valve 21 controlled orifice 22 with manifold vacuum from the engine, not shown, in a manner to be described. Movement of the valve 21 is controlled by a power actuator which, in the form illustrated, is a-differential pressure diaphragm type actuator in which a diaphragm 23 divides a suitable cavity provided for this purpose in the housing 12 and cover 12a into a vacuum chamber 24 and a pressure chamber 25, the valve 21 being secured to the diaphragm 23 for movement therewith. Engine manifold vacuum is supplied to the vacuum chamber 24 through a vacuum conduit or channel 26 in the housing and fluid under pressure is supplied to the pressure chamber 25 through a conduit 27 with flow to the conduit 27 being controlled by a control valve 28 which selectively connects this conduit to a suitable source of fluid under pressure from a passage 30 or to the atmosphere via a passage 31, in a manner to be described. A spring 32 is positioned in the vacuum chamber to abut against the diaphragm 23 to normally bias the diaphragm in a direction to effect unseating of the valve 21 relative to the orifice 22.

Further, in accordance with the invention, the range of movement of the power piston 16 and, therefore, of the main metering rod 10 is controlled as a function of the altitude and of the operating mode for the emission control system of the vehicle through actuation of the control valve 28 in a manner to be described.

To effect the altitude compensation and the emission control mode of operation control, a control lever 33 is pivotably supported intermediate its ends by a pin 34 suitably supported on the housing 12. The control lever 33 has one arm thereof bifurcated at its free end for receiving a pin end 15a of the rod carrier 15 and thereby provides a pair of integral, spaced apart stops, identified as an upper stop 33a and a lower stop 33b, for the rod carrier 15 whereby to limit its movement in either direction as a function of the position of these stops. The opposite end of the control lever 33 operatively engages one end of a reciprocal actuator rod 35. Reciprocal movement of the actuator 35 is effected both by a bellows type aneroid 36 and a differential pressure power actuator, generally designated 38, to be described, positioned in series with each other.

As shown, the aneroid 36 is positioned in a well 37 provided in housing-12 and which is in communication at all times with the atmosphere, whereby the bellows of this aneroid will expand or contract as a function of the barometric pressure which, of course, varies as a function of altitude. The aneroid thereby acts as a link of predetermined varying length depending upon barometric pressure between the power actuator 38 and the control lever 33 via actuator rod 35.

In the embodiment illustrated, the power actuator 38 is a diaphragm-type actuator including a flexible diaphragm 40 having one end of an actuator stem 41 fixed thereto, the opposite end of the stem 41 abutting against and supporting the aneroid 36, the diaphragm being positioned to divide a cavity provided in the for example, a predetermined 14/1 air-fuel mixture to the engine.

However, if the mode of operation of the emission control system is changed from the converter mode to the reactor mode in the manner described in the aboveidentified US. Pat. applications Ser. Nos. 312,574 and 312,567, while the vehicle is still operating at sea level, the control valve 28 would be actuated to then connect the power actuator 38 and valve 21 control unit to atmospheric pressure so that the diaphragms 40 and 23 would be moved down, the latter effecting unseating of valve 21 to, in effect, free the power piston 16 to give a 16/1 to 12/1 fuel ratio depending on manifold vacuum, since the upper and lower stops 33a and 3317, re spectively, limit travel of the power piston in opposite directions. The elements of this linkage arrangement would then be positioned as shown in FIG. 3 with the upper stop 33a and lower stop 33!) now moved up relative to their original positions, shown in FIG. 1.

While still operating at sea level and in either the converter mode or the reactor mode of the emission control system operation, at wide open throttle conditions, the power enrichment system of the carburetor would operate when the secondary throttle valves of the carburetor are opened in addition to operation of the main metering system so that a full power composite air-fuel mixture of 12/ 1, for example, would be supplied to the engine under these wide open throttle conditions, seen by the graphs in FIGS. 2 and 4.

When operating at altitude as, for example, at an altitude of 5,000 feet, the bellows of aneroid 36 would ex pand to effect an overall increase in the length of this element whereby to effect an altitude compensation in the length of the linkage between the actuator 38 and lever 33 and, therefore, to effect the positioning of the stops 33a and 3312 when operating during either the converter mode of operation, as seen in FIG. 5, or dur ing the reactor mode of operation, as seen in FIG. 7, the operation of and the positions of the metering control elements in these FIGS. 5 and 7 corresponding to those previously described with reference to FIGS. 1 and 3, respectively, but compensated for elevation in the FIGS. 5 and 7.

With the elements positioned, shown in FIG. 5, during the converter mode of exhaust emission control operation, and with no manifold vacuum being applied to the power piston 16, a maximum 14/1 air-fuel mixture would be supplied to the engine, as shown by the graph in FIG. 6. However, when in the reactor mode of operation, as seen in FIG. 7, the power piston 16 would then be free to be acted upon by manifold vacuum to move the metering rod to supply a 16/1 to 12/1 mixture depending on manifold vacuum, as seen by the graph in FIG. 8. Under these conditions, in either the converter mode or reactor mode of operation, full power composite mixtures of 1 1/1 only would be achieved, as seen by the graphs in FIGS. 6 and 8, when the secondaries of the carburetor are open, this mixture being provided with no altitude compensation for the power enrichment system of the carburetor.

An embodiment of the subject metering control, described with reference to FIGS. 1, 3, 5 and 7, incorporated into an otherwise conventional four-barrel, two-stage carburetor, is shown in FIGS. 9, 10 and 11. As illustrated, a pair of main metering rods 10 are positioned in main metering wells, not shown, in the float bowl housing 12 of the carburetor to operate in main metering jet orifices, not shown. The main metering rod carrier 15, of generally T-shape, is suitably fixed intermediate its ends to the main power piston 16 as by a fastener 46. The metering rods 10 are suitably secured to the cross arm end 1512 of the carrier 15 as by having the hooked upper end of each metering rod inserted through a suitable opening provided for this purpose in the upright, flanged ends of the cross arm. A U- shaped slot is also provided in the cross arm 15b of the carrier to slidably receive the shoulder of a shoulder screw 50 threaded into the housing 12 whereby the head 50a of the screw 50 will act as a stop to limit upward movement of the rod carrier 15 and therefore power piston 16, as desired. The power piston 16 is moved axially in a piston bore 17 in the housing 12 as acted on by the spring 18 and manifold vacuum, the flow of which is controlled by the valve 21 in the same manner as described with reference to FIGS. 1, 3, 5 and 7.

As best seen in FIGS. 9 and 10, the pivot lever previously identified by reference character 33 is a twopiece lever consisting of lever arms 51 and 52 operatively interconnected as by being fixed for rotation with the pin 34, shown as a two-piece pin threadingly interconnected into a unitary pin, journalled for pivotal movement relative to the housing 12 as, for example, by being rotatively journalled in the bored intermediate wall of a spacer housing 120, which may be formed as an integral part of the housing 12 or, as shown, as a separate element fixed to the housing 12. In this manner, the lever arms 51 and 52 are fixed to pivot as an integral assembly about the pivotal axis of the pin 34. As shown, the lever 51, fixed at one end to the pin 34, has its other end bifurcated to provide the pair of stops 33a and 33b to engage the end 15a of the carrier 15. The lever 52 is also fixed at one end to the pin 34, as by being fixed between the two parts of this pin, and has its other end provided with an outward turned flanged portion 52a extending from one side thereof, the portion 520 being centrally domed and apertured, as at 52b, to socketably receive the upper conical portion of the actuator rod 35. Lever arm 52 is normally biased in a clockwise direction with reference to FIG. 10 by means of a coiled spring 53 encircling the pin 34 with one end of the spring being fixed in a suitable manner to the housing 12c and the opposite end of the coiled spring is hooked over the lever arm 52. The force of spring 53 should be just enough to bias lever arm 52 in a direction to follow the downward movement of the actuator rod 35.

Again referring to FIG. 10, to permit axial length adjustment between the actuator 38 and the lever arm 52 for proper calibration of the carburetor, the actuator rod 35 is threaded at one end into an axial extending internally threaded boss at the upper end of the aneroid 36, the upper end of the actuator rod 35 extending through the lever arm 52 being provided with a slot recess, for example, to receive a tool, such as a screwdriver, to effect axial adjustment of the actuator rod 35 relative to the aneroid 36. At its bottom end, the aneroid 36 is provided with a domed recess to socketably receive the complementary-shaped free end of the stem 41 fixed to the diaphragm 40 of the power actuator 38.

Again referring to FIG. 10, a cover 12d fixed to the spacer housing is used to act as a stop against which the upper portion of stop 33a of the lever arm 51 will housing 12 and cover 12b into an atmospheric pressure chamber 42 and a pressure chamber 43 on opposite sides of the diaphragm. Chamber 42 is connected by a passage 44, through which stem 41 slidably extends, with the well 37 that is in communication with the atmosphere, as previously described. Pressure chamber 43 is connected by a branch conduit 27a to the conduit 27, previously described. A spring 45 is positioned in the pressure chamber 42 to abut against the diaphragm to normally move the diaphragm and, therefore, the stem 41, aneroid 36 and actuator rod 35 in a direction to effect counterclockwise movement of the bifurcated end of control lever 33, for a purpose to be described.

Valve 28 is operable to selectively connect conduit 27 and, therefore, chamber 25 of the valve 21 control unit and the pressure chamber 43 of the power actuator 38 either with the atmosphere through passage 31 or to a source of fluid, such as air under pressure, through passage 30, as by having this passage connected to the output side of the conventional engine driven air pump, not shown, used to supply air at a predetermined pressure above atmospheric pressure to the air injector portion of the exhaust emission control system for the engine, not shown.

The spring 32 and the diaphragm 23 of the valve 21 control unit are properly sized so that when manifold vacuum is applied to one side, the chamber 24 side of the diaphragm, and atmospheric pressure is applied to the opposite or chamber 25 side of the diaphragm, the spring 32 will move the diaphragm 23 and, therefore, valve 21 to the unseated position relative to the orifice 22, the position shown in FIGS. 3 and 7, whereas when air at a pre-selected pressure above atmospheric pressure, as supplied by the air pump, is admitted into the chamber 25, the diaphragm 23 will move in a direction to effect seating of the valve 21 relative to the orifice 22, the position as shown in FIGS. 1 and 5.

In a similar manner, the spring 45 and the diaphragm 40 of actuator 38 are so sized that when air at a preselected pressure above atmospheric,as supplied by an air pump, not shown, is admitted to chamber 43, the

diaphragm 40 will move against the biasing action of spring 45 and the atmospheric pressure in chamber 42 to the position shown in FIGS. 1 and 5, thus moving stem 41 and aneroid 36 axially upward to effect pivotal movement of lever 33 in a clockwise direction to the positions of this lever shown in these figures, whereas when the fluid in chamber 43 is at atmospheric pressure, spring 45 can then bias the diaphragm 40 downward to the position shown in FIGS. 3 and 7, thereby permitting the lever 33 to pivot in a counterclockwise direction from the position shown in FIGS. 1 and 5 to the position shown in FIGS. 3 and 7.

The control valve 28 may be any suitable type valve and any suitable power source can be used to effect its operation. For example, a vacuum motor may be. employed to actuate the valve with the vacuum supplied to the vacuum motor being regulated by a solenoid control valve or, the valve 28 may, itself, be a solenoid control valve which is energized by a suitable sensor circuit responsive to control parameters, such as temperature in a converter unit of the emission control system, engine temperature, which may be correlated to the temperature in the converter unit, or engine speed, in the manner described in the above-identified US. Pat. applications Ser. No. 312,574 and Ser. No. 312,567, providing a signal source effecting a change from one mode of emission control operation to another mode of emission control operation.

Thus, assuming the operational position of valve 28 is controlled by a solenoid, the solenoid could be deenergized when the exhaust emission control system is in the converter mode with the movable element of the control valve 28 then being in the position shown in FIGS. 1 and 5. When the exhaust emission control system is operating in the reactor mode, the solenoid would then be energized to move the movable element of the control valve 28 to the control position shownin FIGS. 3 and 7. It is only necessary that the control valve 28 be operable to connect the pressure chamber 25 of the valve 21 control unit and the chamber 43 of the actuator 38 to a source of fluid above atmospheric pressure when the exhaust emission control system is operating in a converter mode and then to connect these chambers to the atmosphere when the exhaust emission control system is operating in the reactor mode.

Reference is had to the above-identified U.S. Pat. applications Ser. No. 312,574 and Ser. No. 312,567 for a disclosure of a suitable type sensor and control circuit to effect operation of the carburetor, as through a solenoid to effect actuation of control valve 28, and to effect operation of other components of the tri-mode emission control system, the disclosure of these patent applications being incorporated herein by reference. However, for purposes of this disclosure, a suitable control circuit for only the solenoid SOL-l actuator for the valve 28 is shown schematically in FIG. 1, only, and includes a normally open temperature responsive switch SW.-l and a normally open switch SW-2 responsive to engine speed as by having this switch in the form of a pressure responsive switch connected to a governor pressure tap in the automatic transmission. not shown, of the vehicle in a known manner, the switches SW-l and SW-2 being connected in parallel with re spect to each other between the solenoid SOL-1 and the vehicle battery B-l through an ignition switch SW-3.

In operation, the above described linkage and T- MECS metering control limits the amount of fuel supplied to the engine by the main metering system of the carburetor as a function of the ambient barometric pressure and the operating mode of the exhaust emission control system for the engine through the control of both the operation of the power piston and by limiting the axial movement of the power piston, as desired, to provide predetermined air-fuel mixtures to the engine.

For example, during operation of the engine at sea level, the bellows of the aneroid 36 are not extended so that with the exhaust system operating in the converter mode, and with the movable element of valve 28 positioned whereby fluid above atmospheric pressure is supplied to both the actuator 38, to effect movement of the diaphragm 40 upward against the biasing action of spring 45, and to the control unit for valve 21, to position this valve so that no manifold vacuum is applied to the power piston 16, the elements of the meter control would be positioned as shown in FIG. 1. The upper stop 33a of lever 33 is thus positioned to limit upward movement of the power piston 16 under the bias of spring 18 to an upper limit position whereby the fuel supplied to the engine during main fuel metering in this mode of operation would be in accordance with the graph shown in FIG. 2 and would be such as to provide,

engage to thereby limit clockwise movement of the lever arms 51 and 52 as biased by the spring 53.

What is claimed is:

l. A fuel metering control for the carburetor of an internal combustion engine for an automotive vehicle, the carburetor having a housing with at least one main fuel metering jet therein, the flow through which is controlled by a metering rod fixed by a rod carrier to a main power piston reciprocally journallcd in a piston bore in the housing responsive to engine manifold vacuum, said fuel metering control including a fluid pressure actuated valve means operable to control manifold vacuum flow to the main power piston, movable stop means operatively positioned to limit axial movement of the power piston in opposite directions, a differential fluid pressure power actuator, linkage means operatively connecting said differential fluid pressure power actuator to said stop means to effect movement of said step means and, valve controlled conduit means operatively connected to said valve means, to said power actuator and selectively connectable to a source of a first fluid and to a source of a second fluid under pressure greater than the pressure of said first fluid whereby said valve controlled means selectively supplies a first fluid and a second fluid to said valve means and to said power actuator, said valve controlled conduit means being operative as a function of engine operation to control the flow selectively of said first fluid and of said second fluid to said valve means and to said power actuator whereby said fuel metering control will be operative in the carburetor to provide dual fuel mixtures to the engine as a function of engine operating conditions.

2. A fuel metering control according to claim 1 wherein said linkage means includes a bellows-type aneroid operative as a function of barometric pressure to vary the effective length of said linkage means connection between said power actuator and said stop means.

3. A fuel metering control according to claim 2 wherein said stop means includes a lever pivotally mounted on the housing with one end of said lever operatively connected to said linkage means and the opposite end of said lever being bifurcated to provide an upper stop and a lower stop in spaced relation to each other and positioned in the path of movement of the rod carrier to thereby limit axial movement of the power piston as a function of the position of said upper stop and said lower stop.

4. A fuel metering control according to claim 1 wherein said valve means includes a diaphragm forming with a cavity in the housing a first chamber operatively connected to receive engine manifold vacuum and a second chamber operatively connected to said valve controlled conduit means, passage means in the housing connecting said first chamber to the piston bore, a valve fixed to said diaphragm for movement therewith between a first position in which said valve is seated relative to said passage means to block flow therethrough and a second position in which said valve is unseated relative to said passage means to permit flow therethrough and, spring means operatively connected to said diaphragm to normally bias said diaphragm in a direction to move said valve to said second position.

5. A fuel metering control for the carburetor of an internal combustion engine equipped with an exhaust emission control system operative selectively in at least a converter mode and a reactor mode of operation, the carburetor having a housing with at least one main fuel metering rod axially positioned therein by a rod carrier fixed to a main power piston for axial movement therewith, relative to a main fuel metering jet in the housing, the power piston being responsive to engine manifold vacuum acting against the biasing action of a power piston spring, said fuel metering control including a control valve positioned to control manifold vacuum flow to the power piston, a differential fluid pressure actuator operatively connected to said valve to effect posi tioning of said valve between a first position blocking manifold vacuum flow to said power piston and a second position permitting manifold vacuum flow to said power piston, a lever pivotally mounted adjacent to said power piston with one end of said lever having spaced apart stops thereon positioned in the path of travel of the rod carrier to limit its axial movement in opposite directions, a differential fluid pressure power actuator and an aneroid mounted in series with each other within the housing and operatively connected to the opposite end of said lever, both said pressure actuator and said power actuator being selectively connectable by a valved conduit to a source of fluid under a first pressure and to a source of fluid under a second pressure as a function of the operating mode of the emission control system whereby said carburetor will provide the proper air-fuel ratio when the emission control system is operating in the converter mode and to provide an air-fuel ratio for optimum economy when the emission control system is operating in the reactor mode. 

1. A FUEL METERING CONTROL FOR THE CARBURETOR OF AN INTERNAL COMBUSTION ENGINE FOR AN AUTOMOTIVE VEHICLE, THE CARBURETOR HAVING A HOUSING WITH AT LEAST ONE MAIN FUEL METERING JET THEREIN, THE FLOW THROUGH WHICH IS CONTROLLED BY A METERING ROD FIXED BY A ROD CARRIER TO A MAIN POWER PISTON RECIPROCALLY JOURNALLED IN A PISTON BORE IN THE HOUSING RESPONSIVE TO ENGINE MANIFOLD VACUUM, SAID FUEL METERING CONTROL INCLUDING A FLUID PRESSURE ACTUATED VALVE MEANS OPERABLE TO CONTROL MANIFOLD VACUUM FLOW TO THE MAIN POWER PISTON, MOVABLE STOP MEANS OPERATIVELY POSITIONED TO LIMIT AXIAL MOVEMENT OF THE POWER PISTON IN OPPOSITE DIRECTIONS, A DIFFERENTIAL FLUID PRESSURE POWER ACTUATOR, LINKAGE MEANS OPERATIVELY CONNECTING SAID DIFFERENTIAL FLUID PRESSURE POWER ACTUATOR TO SAID STOP MEANS TO EFFECT MOVEMENT OF SAID STOP MEANS AND, VALVE CONTROLLED CONDUIT MEANS OPERATIVELY CONNECTED TO SAID VELVE MEANS, TO SAID POWER ACTUATOR AND SELECTIVELY CONNECTABLE TO A SOURCE OF A FIRST FLUID AND TO A SOURCE OF A SECOND FLUID UNDER PRESSURE GREATER THAN THE PRESSURE OF SAID FIRST FLUID WHEREBY SAID VALVE CONTROLLED MEANS SELECTIVELY SUPPLIES A FIRST FLUID AND A SECOND FLUID TO SAID VALVE MEANS AND TO SAID POWER ACTUATOR, SAID VALVE CONTROLLED CONDUIT MEANS BEING OPERATIVE AS A FUNCTION OF ENGINE OPERATION TO CONTROL THE FLOW SELECTIVELY OF SAID FIRST FLUID AND OF SAID SECOND FLUID TO SAID VALVE MEANS AN TO SAID POWER ACTUATOR WHEREBY SAID FUEL METERING CONTROL WILL BE OPERATIVE IN THE CARBURETOR TO PROVIDE DUAL FUEL MIXTURES TO THE ENGINE AS A FUNCTION OF ENGINE OPERATING CONDITIONS.
 2. A fuel metering control according to claim 1 wherein said linkage means includes a bellows-type aneroid operative as a function of barometric pressure to vary the effective length of said linkage means connection between said power actuator and said stop means.
 3. A fuel metering control according to claim 2 wherein said stop means includes a lever pivotally mounted on the housing with one end of said lever operatively connected to said linkage means and the opposite end of said lever being bifurcated to provide an upper stop and a lower stop in spaced relation to each other and positioned in the path of movement of the rod carrier to thereby limit axial movement of the power piston as a function of the position of said upper stop and said lower stop.
 4. A fuel metering control according to claim 1 wherein said valve means incLudes a diaphragm forming with a cavity in the housing a first chamber operatively connected to receive engine manifold vacuum and a second chamber operatively connected to said valve controlled conduit means, passage means in the housing connecting said first chamber to the piston bore, a valve fixed to said diaphragm for movement therewith between a first position in which said valve is seated relative to said passage means to block flow therethrough and a second position in which said valve is unseated relative to said passage means to permit flow therethrough and, spring means operatively connected to said diaphragm to normally bias said diaphragm in a direction to move said valve to said second position.
 5. A fuel metering control for the carburetor of an internal combustion engine equipped with an exhaust emission control system operative selectively in at least a converter mode and a reactor mode of operation, the carburetor having a housing with at least one main fuel metering rod axially positioned therein by a rod carrier fixed to a main power piston for axial movement therewith, relative to a main fuel metering jet in the housing, the power piston being responsive to engine manifold vacuum acting against the biasing action of a power piston spring, said fuel metering control including a control valve positioned to control manifold vacuum flow to the power piston, a differential fluid pressure actuator operatively connected to said valve to effect positioning of said valve between a first position blocking manifold vacuum flow to said power piston and a second position permitting manifold vacuum flow to said power piston, a lever pivotally mounted adjacent to said power piston with one end of said lever having spaced apart stops thereon positioned in the path of travel of the rod carrier to limit its axial movement in opposite directions, a differential fluid pressure power actuator and an aneroid mounted in series with each other within the housing and operatively connected to the opposite end of said lever, both said pressure actuator and said power actuator being selectively connectable by a valved conduit to a source of fluid under a first pressure and to a source of fluid under a second pressure as a function of the operating mode of the emission control system whereby said carburetor will provide the proper air-fuel ratio when the emission control system is operating in the converter mode and to provide an air-fuel ratio for optimum economy when the emission control system is operating in the reactor mode. 